Nowadays, it is commonly seen that backlight modules are used for electronic devices with flat panel displays, which includes devices as small as hand-held palm pilots and as large as big-screen TVs. A typical backlight consists of a light source, such as Cold Cathode Fluorescent Lamp (CCFL) or Light Emitting Diodes (LED), a light guide, a diffuser, and a brightness enhancement film. The design challenge of a backlight module is to generate uniform illumination across the LCD surface and luminance that is high enough to produce good contrast in a day environment (so that you can see the display of a laptop computer or a handheld electronic device, for example, with the room lights on), by the cooperation of the diffuser and the brightness enhancement film. Although, Taiwan is now one of the three major production countries for Notebook PCs, the critical component, backlight modules, still has to be imported and there is a heavy reliance on foreign providers. Thus, it is imperative for Taiwan to establish the design and production technology. Moreover, a conventional backlight usually consists of a plurality of optical films, which is the cause of low luminous efficacy, high manufacture cost and low assembly yield, and so on.
Please refer to FIG. 1, which is a perspective view of a luminance control film assembly disclosed in U.S. Pat. No. 6,091,547, entitled “Luminance Control Film”. The luminance control film assembly of FIG. 1 is the formation of stacking a luminance control film 12 on top of another luminance control film 10, which can control and guide incident light to collimate for achieving the objects of improving on-axis luminance. However, the disclosed luminance control film is capable of collimating light effectively, it is disadvantageous by being able to diffuse incident light sufficiently enough to produce uniform illumination.
Please refer to FIG. 2, which is a cross-sectional view of a light-diffusing sheet disclosed in Japan. Pat. No. 2001324608, entitled “Light-Diffusing Sheet”. The light-diffusing sheet of FIG. 2 is substantially a layer of resin 24 formed on a transparent substrate 20 with a plurality of resin particles 22 of different diameter dispersed therein, which enables incident light to be scattered and thus diffused, but is disadvantageous by the effect of reducing luminous efficiency caused by the light-scattering of the plural particles 22.
Therefore, it is in great demand to have an improved light modulation element capable of overcoming the shortcomings of prior arts.